The invention concerns a vane-cell pump in accordance with the features of the independent claim.
DE 33 33 647 A1 discloses a vane-cell pump having these structural features whose construction guarantees that the amount and pressure of a liquid medium to be supplied, e.g. lubricant for pressure lubrication, are automatically adjusted to the requirements and the respective state of a unit to be lubricated, e.g. a combustion engine.
Towards this end, the stator, which can be pivoted radially relative to the rotor for pressure control, is correspondingly displaced by an actuator. An actuating piston of the pressure regulating device is guided in a guiding cylinder of the pump bearing housing and acts on the actuator. The cylinder space is thereby in permanent communication with the pressure side of the vane-cell pump via a channel. The pressure regulating device has at least one pressure spring, forming a stop and acting on the actuator as a counter force in opposition to the piston. It is supported on one side by the bottom of a further guiding cylinder which is coaxial to the guiding cylinder of the actuating piston, and on the other side by a counter piston guided therein and communicating with the actuator.
Corresponding pretension of the pressure spring of the pressure regulating device adjusts the supply pressure in dependence on the spring characteristics.
The pressure regulating device of this known vane-cell pump requires a significant degree of technical and assembly effort with a correspondingly large amount of space being required for accommodating the two coaxially guided actuating and counter pistons in the pump bearing housing.
It is therefore the underlying purpose of the invention to substantially simplify the construction of the pressure regulating device for vane-cell pumps of the type recited in the independent claim.
This object is achieved with a vane-cell pump having the features of the independent claim.
In the inventive construction, the pressure regulating device comprises only one actuator in the form of a pivot piston guided in the guide of the pump bearing housing in a pressure and liquid-tight fashion which is directly loaded by the pressure medium. The stored energy can act directly as a counter force on the pump stator e.g. at a suitable location in the bearing housing.
In the most simple form, the inventive construction requires only one single pressure and liquid-tight pivotable actuator for controlled pivoting of the pump stator and at least one energy accumulator which can be accommodated in the pump bearing housing at a freely selectable location relative to the pump stator.
The pump stator can thereby form a one-armed or two-armed lever wherein, in the latter case, the lever arm facing away from the pump rotor can form the pivot piston.
The pivot piston will preferably be operated in opposition to at least one pressure spring which is supported thereon to produce the stored energy.
This accumulated energy can thereby vary to permit variable adjustment of the maximum supply pressure.
This can be effected by serially switching pressure springs in steps or by providing a pressure spring which can be gradually pretensioned.
The pump stator can be disposed in the bearing housing on a pivot axis which is fixed to the housing or, with a partially cylindrical hinge section provided between its two lever arms, can be brought into positive engagement with two mutually opposite bearing surfaces of the pump bearing housing which are fixed to that housing.
The essential features and details of the invention can be extracted from embodiments of vane-cell pumps which are shown in the drawings in an exemplary and simplified fashion.